Doping of a high calcium oxide metaphosphate glass with titanium dioxide

Abstract

This study investigates the effect of doping a high calcium oxide containing metaphosphate glass series (CaO) 40 (Na 2 O) 10 (P 2 O 5 ) 50 with TiO 2 (1, 3, and 5 mol%). TiO 2 incorporation increased the density and glass transition temperature while reduced the degradation rate (5 mol% in particular) by twofold compared with (CaO) 30 system reported previously. This has been confirmed by ion release and the minimal pH changes. TiP 2 O 7 , NaCa(PO 3 ) 3 and CaP 2 O 6 phases were detected for all TiO 2 -containing ceramics. XPS showed that the surface is composed of Ca, P, and Ti. Ti was recognized mainly as TiO 2 , but its total amount was lower than theoretical values. 31 P magic angle spinning (MAS) NMR showed a downfield shift of the 31 P lineshape with increasing TiO 2 , interpreted as an effect of the titanium cation rather than an increase in the phosphate network connectivity. FTIR showed that incorporation of TiO 2 increased the strength of the phosphate chains, and the O/P ratio while introducing more Q 1 units into the structure at the expense of the Q 2 units. There were no differences, however, in surface topography roughness and free energies between these glasses. These results suggested that TiO 2 and CaO were acting synergistically in producing glasses with controllable bulk and structural properties.